1. Field of the Invention
The present invention relates to a television camera provided with a test pattern projecting apparatus fixedly or detachably mounted on the objective lens.
2. Description of the Prior Art
The color television cameras currently employed for broadcasting are mostly of three-tube type and require a series of adjusting operations in order to assure a satisfactory color quality at the replacement of television tubes, at the periodical maintenance and prior to starting use. Such adjustments have been achieved by illuminating a test pattern for inspecting control items such as resolution, registration, gray scale etc., forming the image of said test pattern through the objective lens onto the television tube, framing said image to a standard size and adjusting the CCU (Color Control Unit) which is partially located on the camera while observing thus formed image. The projection of such test pattern has usually been achieved by illuminating a test pattern of translucent type or reflective type with outdoor light. Such method, however, requires time and cumbersome operations since the conditions of test pattern setting has to be determined each time.
Besides, although the color television cameras have shown remarkable improvements in stability, they often require, even during the use thereof, a temporary check with a test pattern which is difficult to achieve with the above-mentioned method.
In order to resolve such drawback and to improve the function of color television cameras there has been proposed a method of incorporating a test pattern projecting apparatus in a zoom lens which constitutes the objective lens of the television camera, but such apparatus has only been used for auxiliary purpose because of unsatisfactory performance thereof.
One of such unsatisfactory performances lies in the difficulty of forming a pattern image of a desired color temperature on the television tube.